When Origin Energy approached Northern Territory pastoralist Rod Dunbar in 2014 with a request to build a test gas well on his property, he was deeply concerned.

During negotiations over the next three years, that concern turned to alarm as he discovered more about the company's proposal for his 405,000 hectare cattle station, 500 kilometres south-east of Darwin.

Origin's own environmental report assessing the risks of drilling test wells at several sites on the Beetaloo Basin, said fracking — the method of extracting the gas — could pose a risk of causing aquifers under his property to leak into each other.

Origin's report rated the risk of leakage as "medium to high, and likely" with "serious consequences".

That was enough for Mr Dunbar. Despite assurances by the company, he refused Origin's request to drill a test well.

"If another aquifer's got a high salt content, or some other content in it, it could damage the aquifer that we're using to water 25,000 cattle," he said.

Opposite sides of NT's fracking debate

The NT Labor Government is grappling with whether to lift the fracking moratorium it brought in last August as a key election commitment.

Lifting the moratorium would unlock the huge reserves of gas discovered in the Beetaloo Basin, where Mr Dunbar and Mr Sullivan farm.

"The state of the Territory economy is such that I don't think we can afford to say, 'We're not going to look at this resource, we're going to leave it there, and not do anything with it'," Mr Sullivan said.

The fracking industry has promised up to a billion dollars worth of investment in the NT, including remote roads, and up to 6,000 jobs.

But many landholders believe the companies and the NT Government still have outstanding environmental questions to answer.

Origin Energy's chief geologist and unconventional exploration manager David Close said once the company identified the risks in its report, it developed solutions to mitigate them, including specially designed steel well casings.

It used these last year to drill the test well on the Amungee Mungee Station Station, which confirmed there is at least 6.6 trillion cubic feet of gas in the Beetaloo Basin.

"What Origin did was engineer and design our [well] casing so there was no possibility for crossflow between those two aquifers. That risk was eliminated through engineering," Mr Close said.

"We are constantly monitoring to ensure that the gas coming out of the well bore is only coming up through the production casing and there is no pressure or gas released anywhere else."

No guarantee abandoned wells won't leak

But Mr Ross is questioning how the gas companies can guarantee that abandoned wells will never leak.

"Nothing lasts forever. Where they're going down to is acidic, and steel won't last once it's in contact with water and acidic material. It will start deteriorating. We see that with our own water bores. And these companies won't be around to fix it," Mr Ross said.

Origin's environmental report said there could be a small risk of water or gas leaking from deep formations into freshwater aquifers through abandoned wells.

Mr Close said Origin was sure its wells would remain sound once they were filled with concrete and abandoned.

"Even if there was degradation at the very near surface that does not extend into the deep sub-surface," he said.

"I don't know if any scientist will ever tell you that anything lasts forever.

"We risk assess. We design. We expect that this will have integrity for the life required of the well, similar to the rock formations around them."

Rod Dunbar is also concerned that the question of who would compensate for any environmental damage, after gas projects conclude, has not yet been resolved.

"Damage may not be apparent until some time after an actual incident," he said.

Mr Close said Origin would insure farmers against environmental damage for the life of projects and their remediation, but the NT Government will have to decide what happens after that.

Chief Minister Michael Gunner has committed to waiting until after his Government's independent inquiry into the risks and benefits of fracking reports some time this year, before deciding whether to lift the moratorium.